1. Field of the Invention
The present invention relates generally to a tension-adjusting device for a chain in a chain saw without using any auxiliary tool.
2. The Prior Arts
A chain saw is a popular power tool and is generally used in sawing trees or boards. However, after a long-term use, a chain of the chain saw often gets loosed. When the chain is too loose, it may be come off the chain saw during sawing, resulting in an obstacle in operation. Such a situation will also reduce the life of a chain saw. In conventional chain saws, an operator adjusts the tension of chain by using an auxiliary tool to make the chain tensioned again on the sprocket of the chain saw. However, if the chain is too tense, it may be broken and thus produce a serious accident. Therefore, the operator needs to adjust the tension of chain again by using the auxiliary tool to a proper extent. Using an auxiliary tool to adjust the tension of chain is troublesome and time-consuming, and this also greatly reduces the efficiency of sawing. Further, it is inconvenient for the operator to additionally carry the auxiliary tool.
Therefore, it is necessary to propose an improved tension-adjusting device for a chain in a chain saw. Taiwan Patent Publication No. 503,810 discloses a device for adjusting a chain saw, which comprises an adjusting assembly, a driving assembly and a fixing base. The adjusting assembly comprises a dust-proof cover, a driving disk and a knob; the driving assembly comprises a guide piece, a position piece, a brake disk and a toothed disk; and the fixing base comprises a sprocket, a screw and a guide block. By rotating the knob to drive the driving disk, the tension adjustment of chain can be attained. When the driving disk is driven to rotate, the brake disk follows to be rotated simultaneously and thus, the spiral guide rail provided under the brake disk pushes the position piece to move along the guide block to adjust the tension of chain.
However, in the conventional tension-adjusting device for a chain saw, the adjusting assembly and the driving assembly comprise many parts, and the driving disk and the toothed disk have a complicated structure, resulting in assembly and maintenance difficult and thus having higher manufacturing cost.